Total hip replacement surgery involves the introduction of an artificial hip joint in a patient. The artificial hip joint typically consists of a pelvic implant and a femoral implant. The pelvic implant is a cup received in the acetabulum. The femoral implant consists of a spherical portion received at an end of a longitudinal implant portion. The longitudinal implant portion is introduced into the intramedullary canal of the resected femur, with the spherical portion being generally centered with respect to the previous position of the femoral head. Therefore, the femoral head (i.e., spherical portion of the femoral implant) and the cup (i.e., pelvic implant) coact to create the artificial hip joint.
Different output values are of concern in hip replacement surgery. In order to reproduce a natural and/or improved gait and range of motion to a patient, the position and orientation of the implants, the offset of the femur and the limb length must be considered during surgery. The work of the surgeon during hip replacement surgery will have a direct effect on these output values.
Known computer-aided hip replacement surgery techniques presently involve preoperative computerized tomography (CT) steps that enable acquisition of data related to the skeletal configuration of the patient. This data is used, for instance, to determine implant size and to guide the surgeon intraoperatively into reproducing the ideal output values mentioned above.
There are inconveniences to the use of CT. Firstly, it is desired to reduce preoperative steps to a minimum. Ideally, hip replacement surgery would be free of preoperative steps, as this would be logistically preferred. Cost saving issues are involved in the logistic simplification of hip replacement surgery. Moreover, CT uses X-rays, which are known to be hazardous to health.
Accordingly, it is believed that computer-aided hip replacement surgery techniques having minimal preoperative steps would be of great appeal to surgeons and to management of health institutions.